Consumers across the UK were urged not to eat Irish pork yesterday after animal feed contaminated with dioxins - carcinogenic chemicals - was traced to farms on both sides of the border.

Last night Irish government officials also admitted that the contaminated pig meat including bacon, sausages and Christmas hams could have been exported to as many as 25 countries, including France and the Netherlands.

The Food Standards Agency (FSA) issued the advice after it emerged that nine farms in Northern Ireland have used the same feed substance that prompted a recall of all pork products processed in the republic following its discovery in pig farms south of the border.

The FSA stressed that its notice was precautionary and said the affected meat did not pose any significant health risk. It said: "The Food Standards Agency is today advising consumers not to eat pork or pork products, such as sausages, bacon, salami and ham, which are labelled as being from the Irish republic or Northern Ireland, while it continues to investigate whether any products contaminated with dioxins have been distributed in the UK.

"From the information that we have at this time, we do not believe there is significant risk to UK consumers, as adverse health effects from eating the affected products are only likely if people are exposed to relatively high levels of this contaminant for long periods."

The scare was triggered after high levels of dioxins were found in slaughtered pigs which had eaten the contaminated feed in the Irish republic.

The food processor company at the centre of the scare, Millstream Power Recycling, in Co Carlow, which recycles food products into pig meal, said last night it was cooperating with government officials to identify the source of the contamination.

All production at the plant, which is owned by Robert Hogg and employs about 15 people, was stopped last week when the possibility of a link between it and the contaminated feed was made. The feed had been supplied to 10 pig farms in the country, prompting the republic's government last night to recall all pork products made since the start of September.

Last night Sainsbury's said it did not sell any bacon, sausages or any other pork products from the republic. A spokeswoman for the supermarket group added that it was investigating whether any Irish pork-based products were on sale in any of its stores, but had no evidence of that.

Tesco said it would offer refunds on all own-brand pork and bacon products. "As a matter of urgency we are checking all our other products just to see if any of them contain Irish pork produce. If they do, obviously we would take immediate action and remove them from shelves."

There are 112 Tesco stores in the Irish republic, all of which, according to a spokesman in Dublin, have removed every pork product from their shelves.

Marks & Spencer said it did not source any fresh pork from Ireland but was working with the FSA and would remove any products if necessary.

The leader of Ireland's farmers yesterday described the scare as "an absolute disaster" for the country's pig sector. Last year Ireland exported €212m (£182m) worth of such products. The president of the Irish Farmers Association, Padraigh Walshe, said it was the greatest crisis in Irish agriculture since foot and mouth.

The contamination came to light last Monday but was only confirmed by Irish government officials on Saturday. Ireland's agriculture minister, Brendan Smith, said an "intensive investigation" had been under way. He confirmed that only one feed supplier was involved.

Last night Ireland's chief veterinary officer, Paddy Rogan, said "certainly less than 30" countries could be affected. France and the Netherlands have notified Dublin that they received contaminated shipments of meat or processed foods which turned out to have originated in Ireland. Belgium received contaminated byproducts, officials said.

The Irish pork tested last week had up to 200 times more dioxins than is considered safe by the World Health Organisation and the European Union.